1. Field of the Invention
This invention relates to fluid pumps and, more particularly, to a pump for providing a pulsed delivery of fluid to a point of use.
2. Background Art
High pressure water has long been used to clean blocked and silted drainage, sewer, and other conduits. Water is pumped through a flexible hose at high pressure and is expelled controllably at a downstream nozzle. Jets on the nozzle direct the discharging water angularly with respect to the hose in a trailing direction.
To effect a cleaning operation, the nozzle, which is normally at the leading end of the hose, is introduced to the sewer or other conduit to be cleaned. The water discharging from the jets propels the nozzle and hose forwardly through the conduit. At the same time, the pressurized water scours the walls of the conduit. If excessive or stubborn buildup is present in the conduit, a leading jet may be provided to propel liquid forwardly to break through any obstruction and define a path for the nozzle.
The above technique is employed using different nozzle and hose types, different flow rates and volumes and different pressures, as the particular job dictates. With this technique, it is possible to penetrate and effectively clean conduits up to 400 feet in length. This length is generally the maximum that is encountered for industrial, municipal, and household applications by reason of the regular access afforded through manholes.
While it may be possible to penetrate longer conduits with the above described technique, this technique may not be adequate where curves, elbows, and traps are encountered and/or when the conduit length significantly exceeds 400 feet. To enhance advancement of the nozzle, particularly through a long, circuitous conduit pathway, and break up obstructions, it is known to interrupt the nozzle flow to produce a pulsed fluid delivery through the nozzle. It is a known principle that repetitive interruption of high pressure flow through a nozzle to cause a pulsating action will result in the nozzle and hose continuing to progress through a conduit over or around obstructions more effectively than can be achieved by the steady pull obtained from a constant rearward expulsion of fluid.
A number of systems have been devised to produce pulsed discharge of a fluid. One such system is shown in U.S. Pat. No. 4,838,768, to Flaherty. Flaherty employs two pistons which alternatingly operate to discharge fluid through an outlet. Pulses from the separate pistons are timed to immediately follow one another. It is also possible to disable one of the pistons to provide a lag between successive pulses by a single one of the pistons.
Overall, the Flaherty system is relatively complicated and, by reason of requiting custom building, may be relatively expensive. There are five check valves in the system and multiple moving pistons. Failure of any element may result in system malfunction. Another problem with the Flaherty system is that it is inherently quite cumbersome by reason of there being multiple pistons and flow passages associated therewith.
The inventor herein designed a pulsating liquid jet apparatus that is the subject of U.S. Pat. No. 5,070,907. This unit has enjoyed ongoing commercial success.
The unit in U.S. Pat. No. 5,070,907, while highly effective, has a number of drawbacks common to systems of similar design. The operation of the unit may be altered when the unit is used to deliver hot water, which is commonly done when it is desired to eliminate a frozen blockage in a conduit. The hot water, which is typically at 140.degree.-160.degree. F., effects the function of the springs within the unit which may result in compromised and/or different performance characteristics for the unit.
Another problem with the above unit is that as the unit capacity is increased, the piston must be proportionately increased in size. Accordingly, it may in some situations be necessary to significantly increase the overall size of the unit. It is always the objective of designers of such systems to minimize their size, due to the fact that the units are commonly transported to and around job sites.
Many other systems are currently known for producing a pulsed delivery of a fluid, but these systems likewise have drawbacks which demonstrate the need for an improved fluid pump.